Are blood transfusions beneficial in the cyclosporine era?

Induction of Foxp3-expressing regulatory T-cells by donor blood transfusion is required for tolerance to rat liver allografts

Background

Donor-specific blood transfusion (DST) prior to solid organ transplantation has been shown to induce long-term allograft survival in the absence of immunosuppressive therapy. Although the mechanisms underlying DST-induced allograft tolerance are not well defined, there is evidence to suggest DST induces one or more populations of antigen-specific regulatory cells that suppress allograft rejection. However, neither the identity nor the regulatory properties of these tolerogenic lymphocytes have been reported. Therefore, the objective of this study was to define the kinetics, phenotype and suppressive function of the regulatory cells induced by DST alone or in combination with liver allograft transplantation (LTx).

Methodology/Principal Findings

Tolerance to Dark Agouti (DA; RT1^a) rat liver allografts was induced by injection (iv) of 1 ml of heparinized DA blood to naïve Lewis (LEW; RT1^l) rats once per week for 4 weeks prior to LTx. We found that preoperative DST alone generates CD4⁺ T-cells that when transferred into naïve LEW recipients are capable of suppressing DA liver allograft rejection and promoting long-term survival of the graft and recipient. However, these DST-generated T-cells did not express the regulatory T-cell (Treg) transcription factor Foxp3 nor did they suppress alloantigen (DA)-induced activation of LEW T-cells in vitro suggesting that these lymphocytes are not fully functional regulatory Tregs. We did observe that DST+LTx (but not DST alone) induced the time-dependent formation of CD4⁺Foxp3⁺ Tregs that potently suppressed alloantigen-induced activation of naïve LEW T-cells in vitro and liver allograft rejection in vivo. Finally, we present data demonstrating that virtually all of the Foxp3-expressing Tregs reside within the CD4⁺CD45RC⁻ population whereas in which approximately 50% of these Tregs express CD25.

Conclusions/Significance

We conclude that preoperative DST, in the absence of liver allograft transplantation, induces the formation of CD4⁺ T-cells that are not themselves Tregs but give rise directly or indirectly to fully functional CD4⁺CD45RC⁻Foxp3⁺Tregs when transferred into MHC mismatched recipients prior to LTx. These Tregs possess potent suppressive activity and are capable of suppressing acute liver allograft rejection. Understanding the mechanisms by which preoperative DST induces the generation of tolerogenic Tregs in the presence of alloantigens may lead to the development of novel antigen-specific immunological therapies for the treatment of solid organ rejection.

Combination of donor-specific blood transfusion with anti-CD28 antibody synergizes to prolong graft survival in rat liver transplantation

Donor-specific blood transfusion (DST) has been shown to effectively induce tolerance to certain allografts. In addition, it is well known that blockade of costimulatory signals reduces the ability of T cells to respond to alloantigens, prolonging allograft survival in some transplant models. We assessed the effects of single or multiple DSTs in the absence or presence of anti-CD28 monoclonal antibodies (mAbs) on graft function and host survival in rat liver transplantation (LTx). Fully MHC-mismatched adult male Dark Agouti (DA) and Lewis (LEW) rats were used as donors and recipients, respectively. Heparinized DA blood was administered to naïve LEW rats 7 days before LTx [DST(-7d)], 14 and 7 days before LTx [DST(1 x 2)], twice a week for 2 weeks prior to LTx [DST(2 x 2)] and once a week for 4 weeks prior to LTx [DST(1 x 4)]. For some experiments, two different monoclonal antibodies (mAb) to rat CD28 (JJ316 and JJ319) were administered in combination with some DST treatments. We found that DST administration induced a time- and dose-dependent increase in host survival. Treatment of LEW rats with JJ316 or JJ319 mAb alone failed to prolong graft survival over untreated rats; however, the combination of DST(1 x 2) with JJ316 or JJ319 mAb induced indefinite survival at 100 days following surgery. We found that this protective effect was associated with increased numbers of splenic CD4+ CD45RC- but not CD4+ CD25+ foxp3+ T-cells in long-term survivors. Our data suggest that the combination of suboptimal DST with CD28 mAb induces donor-specific tolerance that correlates with enhanced numbers of regulatory T-cells.

Development of CD25– regulatory T cells following heart transplantation: Evidence for transfer of long-term survival

Donor-specific heart allograft acceptance can be induced in the MHC-mismatched LEW.1 W to LEW.1A rat by donor-specific transfusions. Whereas the induction phase of tolerance has been studied in detail, its maintenance remained poorly understood. Here, we performed a side-by-side comparison of CD25+ and CD25- splenic T cells of 100-day tolerant rats. Administration of CD25- T cells from tolerant rats to sublethally irradiated recipients transferred long-term graft survival. These CD25- T cells displayed a decreased donor-specific response in the mixed lymphocyte reaction and presented suppressive activity. These CD25- T cells accumulated IFN-gamma, IL-10 and Foxp3 transcripts. The in vitro suppressive activity of CD25- T cells required both cell contact and soluble factors (IL-10 and IFN-gamma). The CD25+ T cells from tolerant rats did not show any modification of their regulatory properties. We show that splenic CD25- T cells of tolerant rats contribute to the maintenance of tolerance following the transplantation. Our data show that regulatory T cells are not restricted to the CD4+ CD25+ T cell subset and provide new insights on the mechanisms of tolerance to allograft following donor cell priming.

Early Presence of Regulatory Cells in Transplanted Rats Rendered Tolerant by Donor-Specific Blood Transfusion

Mechanisms by which donor-specific blood transfusion (DSBT) promotes organ allograft acceptance are unclear. In a rat fully mismatched cardiac allograft model, we found that DSBT alone (without immunotherapy) induces the development of regulatory T cells (DSBT-Tregs) posttransplant, thereby shedding new light in the mechanisms of the transfusion effect. Compartments and timing of expansion, requirements, and phenotype of DSBT-Tregs are unknown. It is generally assumed that some time is necessary before Tregs develop. However, we show-by adoptive transfer from DSBT-tolerant into naive recipients: 1) the presence of DSBT-Tregs at 5 days posttransplant in spleen and lymph nodes; 2) their gradual expansion in these compartments; and 3) their presence in the graft 14 of 30 days posttransplant. DSBT-Tregs are donor specific and do not protect third-party allografts. Splenocytes from DSBT-treated nontransplanted recipients or from transplanted DSBT-untreated (rejecting) recipients do not transfer tolerance, indicating that both DSBT and graft are required for sufficient numbers of DSBT-Tregs to develop. Thymectomy (or splenectomy) before DSBT (not at transplantation) abrogate DSBT-Tregs generation and tolerance, showing that thymus (and spleen) are required for DSBT-Tregs generation (not for expansion/maintenance). In contrast with other Tregs models, DSBT-Tregs activity is not restricted to CD4(+)CD25(+) but to CD4(+)CD45RC(-) cells, whereas CD4(+)CD45RC(+) cells act as effector cells and accelerate rejection. In conclusion, DSBT alone induces-rapidly posttransplant-the development of alloantigen-specific Tregs in lymphoid tissues and in the graft. DSBT, graft, thymus, and spleen are required for DSBT-Tregs generation. DSBT-Tregs in this model are CD4(+)CD45RC(-) (identical to Tregs protecting from autoimmunity in rats).

Prophylactic deoxyspergualin treatment in living-related renal-transplant recipients transfused with donor-specific blood

BACKGROUND

Deoxyspergualin (DSG) prophylaxis has improved long-term graft survival in living-related renal-transplant recipients transfused with donor-specific blood (DST). We examined the influence of acute rejection (AR) on graft survival in these patients.

METHODS

The study groups consisted of either historic control recipients without DSG (group A, n=64, 1985-1989) and recipients with DSG as the initial immunosuppressive agent (group B, n=76, 1989-1995). Both groups received DST from a one-haplotype identical donor and were treated with cyclosporine-based immunosuppression. Rejection was classified into accelerated rejection (Acc, within 5 days), AR (from 6 days-3 months), and late AR (LAR, from 4 months-1 year).

RESULTS

Overall 5-year graft survival rates were significantly higher in group B than group A (89.5 vs. 73.4%, P=0.0070). Each group was then subdivided on the basis of whether or not they had an episode of Acc, AR, or LAR. In group A, 5-year graft survival rate was not affected the presence or absence of Acc (75.0 vs. 73.1%), and it was influenced significantly by the presence or absence of AR (50.0 vs. 85.7%, P=0.0012) or LAR (46.7 vs. 81.6%, P<0.0001). In group B, 5-year graft survival did not change significantly by the presence or absence of Acc (100 vs. 88.7%), AR (81.8 vs. 92.6%), or LAR (81.0 vs. 92.7%).

CONCLUSIONS

Prophylactic use of DSG in living-related renal-transplant recipients treated with DST improves long-term graft survival, even in patients with AR episodes.

Pediatric renal transplantation

Renal transplantation in children is a most rewarding treatment that dramatically changes the overall health and lifestyle of children with ESRD. Complexities in different aspects of renal transplantation in children are obvious. Optimum technical conditions and drug therapy must be provided for the success of renal transplantation. Application of recent advances in immunology and long-term care to clinical transplantation continue to improve graft and patient survival rates. Optimization of growth and development also can be improved with the use of rhGH.

Immunosuppressive peptides corresponding to MHC class I sequences

The induction of tolerance is a long-standing goal in transplantation. Intact MHC molecules, or fragments of them, are being used to render T cells unresponsive both in vitro and in vivo. Elucidation of the mechanisms underlying the effects of these treatments should aid the design of novel therapies for transplantation.

Transplantation immunology

A major function of the immune response is the discrimination of self from nonself. It is this response that must be overcome in transplant rejection. Progress in understanding these basic immune mechanisms has helped to improve clinical outcome and lays the foundation for a new generation of therapies.